package com.baozun.util;


import java.io.File;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Title: 文件MD5计算
 * Project: FAP
 * @author ZLJ摘自网络，经多个第三方MD5软件验证
 * Description: 
 * Copyright: Copyright (c) 2012
 * Company: 万达信息股份有限公司
 */
public class MD5Util {
	/**
	 * 默认的密码字符串组合，apache校验下载的文件的正确性用的就是默认的这个组合
	 */
	protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
	protected static MessageDigest messagedigest = null;
	static {
		try {
			messagedigest = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException nsaex) {
			System.err.println(MD5Util.class.getName() + "初始化失败，MessageDigest不支持MD5Util。");
			nsaex.printStackTrace();
		}
	}


	/**
	 * 适用于上G大的文件
	 * @param file
	 * @return
	 * @throws IOException
	 */
	public static String getFileMD5String(File file) {
		try {
//			ch = in.getChannel();
//			MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
			byte[] bytes = FileUtil.file2ByteArray(file);
			messagedigest.update(bytes);
			return bufferToHex(messagedigest.digest());
		} catch ( Throwable t ) {
			t.printStackTrace();
			return null;
		}
	}


	public static String getMD5String(String s) {
		return getMD5String(s.getBytes());
	}


	public static String getMD5String(byte[] bytes) {
		messagedigest.update(bytes);
		return bufferToHex(messagedigest.digest());
	}


	private static String bufferToHex(byte bytes[]) {
		return bufferToHex(bytes, 0, bytes.length);
	}


	private static String bufferToHex(byte bytes[], int m, int n) {
		StringBuffer stringbuffer = new StringBuffer(2 * n);
		int k = m + n;
		for (int l = m; l < k; l++) {
			appendHexPair(bytes[l], stringbuffer);
		}
		return stringbuffer.toString();
	}


	private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
		char c0 = hexDigits[(bt & 0xf0) >> 4];
		char c1 = hexDigits[bt & 0xf];
		stringbuffer.append(c0);
		stringbuffer.append(c1);
	}
	
	public static void main(String[] args) {
        System.out.println(getFileMD5String(new File("e:/20110326013.jpg")));
        System.out.println(getFileMD5String(new File("e:/20110326013_.jpg")));
    }
}
